Ecophysiological Study on the survival strategy of mudskippers in subtropical mangrove swamps of Oceania

澳大利亚弹涂鱼，周眼鱼_分钟鱼，生活在高潮间带泥滩地区，那里只在大潮期间经历海水泛滥。我们的研究地点通常在一个潮汐周期的小潮期间出现7-12天，贯穿一年。结果表明，洞穴水盐度在8月(旱季)延长后，从3月(雨季结束)的33±5PSU增加到84±7。在这些漫长的复现期里，细小对虾一直呆在洞穴里。实验暴露于淡水(FW)或200%水溶液中并不影响微小对虾的氯化细胞密度。然而，氯细胞的顶端凹陷对FW的反应迅速关闭，但对200%SW的反应不明显。200%SW染毒9-14天后，氯细胞体积明显增大。暴露于200%SW后，血浆钠浓度无明显变化，但暴露后第5天，血浆钠浓度明显下降。暴露于200%SW期间无死亡，而暴露于FW的鱼有50%在4天内死亡。这些结果表明，微小对虾极高的耐盐性是由于其上氯细胞的高密度和适应性肥大所致。在长时间的洞穴禁闭期间，浓缩的海水是鱼类唯一的供水来源，这使得微小对虾能够有效地调节体液中的离子浓度。在整个旱季，微小对虾的性腺都是未成熟的，但在雨季随着时间的推移迅速增长，在1-2月达到最大尺寸。随后，在雨季结束时(3月)，性腺的大小减小。产卵发生在2月份的小潮中。这些结果表明，性腺成熟是由雨季的到来触发的，产卵发生在半月周期。

The Australian mudskipper, Periophthalmus_minutus, inhabits high intertidal mudflat areas that experience seawater inundation only during the high water spring tides. Our study site remained emerged usually for 7-12 days during neap tides in one tidal cycle, throughout a year. As a result, burrow water salinity increased from 33 ± 5 psu in March (end of the rainy season) to 84 ± 7 after an extended period of emersion in August (dry season). P.minutus remained inside its burrow during these long emersion periods. Experimental exposure to either freshwater (FW) or 200% SW did not affect the chloride cell density, of P.minutus. However, apical pits of the chloride cells were rapidly closed in response to FW, but not to 200% Sw, exposure. Chloride cell size significantly increased after 9-14 day exposure to 200% SW. Plasma sodium concentration did not change by the exposure to 200% SW but decreased significantly after 5 days in FW. No mortality occurred during exposure to 200% SW, whereas 50% of FW-exposed fish died within 4 days. These results demonstrate that the exceptionally high salinity tolerance of P.minutus is made possible by the high density and adaptive hypertrophy of the opercular chloride cells. This allows P.minutus to effectively regulate ion concentrations of the body fluids during the extended burrow confinement during which concentrated seawater is the only source of water supply to the fish.The gonads of P.minutus were immature throughout the dry season, but rapidly grew with time during the rainy season, attaining the largest size in January to February. Subsequently, the gonadal size decreased at end of the rainy season (March). Spawning occurred in neap tides in February. These results demonstrated that gonadal maturation is triggered by the advent of the rainy season, and that spawning takes place in a semi-lunar cycle.